U.S. patent application number 14/432498 was filed with the patent office on 2015-09-24 for method and apparatus for cold forming thread rolling dies.
The applicant listed for this patent is ILLINOIS TOOL WORKS INC.. Invention is credited to Thomas S. King, Kenneth R. LeVey, Michael J. Marchese, III.
Application Number | 20150266083 14/432498 |
Document ID | / |
Family ID | 49261772 |
Filed Date | 2015-09-24 |
United States Patent
Application |
20150266083 |
Kind Code |
A1 |
LeVey; Kenneth R. ; et
al. |
September 24, 2015 |
METHOD AND APPARATUS FOR COLD FORMING THREAD ROLLING DIES
Abstract
A method is disclosed for roll forming the face pattern onto a
pattern forming die having a pattern receiving face, using an
initial, and subsequent, pattern forming tool, each with a
generally cylindrical pattern defining surface, by relatively and
sequentially reciprocating and rotating the pattern defining
surfaces and the pattern receiving face while engaging them and
urging them to impress the pattern of the pattern defining surfaces
into the pattern receiving face of the forming die blank. An
apparatus for performing the process is disclosed which includes a
platen for the pattern forming die, initial and subsequent pattern
forming tools each having a generally cylindrical pattern defining
surface, a drive mechanism for relatively and sequentially
reciprocating and rotating the pattern defining surfaces and the
pattern receiving face of the forming die blank, and relative
movement mechanism for engaging the surfaces to impress the pattern
of the pattern defining surfaces of the pattern forming tools into
the pattern receiving face of the forming die blank.
Inventors: |
LeVey; Kenneth R.;
(Winfield, IL) ; Marchese, III; Michael J.;
(Chicago, IL) ; King; Thomas S.; (St. Charles,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ILLINOIS TOOL WORKS INC. |
Glenview |
IL |
US |
|
|
Family ID: |
49261772 |
Appl. No.: |
14/432498 |
Filed: |
September 11, 2013 |
PCT Filed: |
September 11, 2013 |
PCT NO: |
PCT/US2013/059227 |
371 Date: |
March 31, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61708939 |
Oct 2, 2012 |
|
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|
Current U.S.
Class: |
76/4 ;
76/107.1 |
Current CPC
Class: |
B21H 3/06 20130101; B21H
3/02 20130101 |
International
Class: |
B21H 3/06 20060101
B21H003/06 |
Claims
1. A method of roll forming the face pattern onto a pattern forming
die comprising: providing a forming die blank having a pattern
receiving face; providing an initial pattern forming tool having a
generally cylindrical pattern defining surface; relatively
reciprocating and rotating said pattern defining surface of said
initial pattern forming tool and said pattern receiving face of
said forming die blank; engaging said generally cylindrical pattern
defining surface of said initial pattern forming tool with said
pattern receiving face of said pattern forming die; and urging said
generally cylindrical pattern defining surface of said initial
pattern forming tool into said pattern receiving face of said
forming die blank to impress the pattern of said generally
cylindrical pattern defining surface of said initial pattern
forming tool into said pattern receiving face of said forming die
blank.
2. The method of roll forming the face pattern onto a pattern
forming die as claimed in claim 1, the method further comprising:
maintaining a constant force between said engaged generally
cylindrical pattern defining surface of said initial pattern
forming tool and said pattern receiving face of said pattern
forming die during said relative reciprocal and rotational movement
therebetween.
3. The method of roll forming the face pattern onto a pattern
forming die as claimed in claim 2, the method further comprising:
providing a subsequent pattern forming tool having a generally
cylindrical pattern defining surface; relatively reciprocating and
rotating said pattern defining surface of said subsequent pattern
forming tool and said pattern receiving face of said forming die
blank; engaging said generally cylindrical pattern defining surface
of said subsequent pattern forming tool with said pattern receiving
face of said pattern forming die after the pattern of said
generally cylindrical pattern defining surface of said initial
pattern forming tool has been impressed into said pattern receiving
face of said forming die blank; and urging said generally
cylindrical pattern defining surface of said subsequent pattern
forming tool into said pattern receiving face of said forming die
blank to impress the pattern of said generally cylindrical pattern
defining surface of said subsequent pattern forming tool into said
pattern receiving face of said forming die blank.
4. The method of roll forming the face pattern onto a pattern
forming die as claimed in claim 3, the method further comprising:
maintaining a constant force between said engaged generally
cylindrical pattern defining surface of said subsequent pattern
forming tool and said pattern receiving face of said pattern
forming die during said relative reciprocal and rotational movement
therebetween.
5. The method of roll forming the face pattern onto a pattern
forming die as claimed in claim 2, wherein said generally
cylindrical pattern defining surface of said initial pattern
forming tool comprises a spiral thread pattern of ridges defining
roots and crests.
6. The method of roll forming the face pattern onto a pattern
forming die as claimed in claim 3, wherein said generally
cylindrical pattern defining surface of said initial pattern
forming tool comprises a spiral thread pattern of ridges defining
roots and crests, said generally cylindrical pattern defining
surface of said subsequent pattern forming tool comprises a spiral
pattern of ridges defining roots and crests, and the included angle
of said ridges on said generally cylindrical pattern defining
surface of said subsequent pattern forming tool is a greater
included angle than the included angle of said ridges on said
generally cylindrical pattern defining surface of said initial
pattern forming tool.
7. The method of roll forming the face pattern onto a pattern
forming die as claimed in claim 6, wherein the included angle of
said ridges on said generally cylindrical pattern defining surface
of said initial pattern forming tool is thirty degrees (30.degree.)
and the included angle of said ridges on said generally cylindrical
pattern defining surface of said subsequent pattern forming tool is
sixty degrees (60.degree.).
8. The method of roll forming the face pattern onto a pattern
forming die as claimed in claim 1, the method further comprising:
maintaining said die blank stationary and rotating and
reciprocating said initial pattern forming tool relative
thereto.
9. The method of roll forming the face pattern onto a pattern
forming die as claimed in claim 3, the method further comprising:
maintaining said die blank stationary and rotating and
reciprocating said initial pattern forming tool and said subsequent
pattern forming tool relative thereto.
10. The method of roll forming the face pattern onto a pattern
forming die as claimed in claim 6, the method further comprising
maintaining said die blank stationary and rotating and
reciprocating said initial pattern forming tool and said subsequent
pattern forming tool relative thereto.
11. The method of roll forming the face pattern onto a pattern
forming die as claimed in claim 3, the method further comprising:
providing a forming die blank having an additional, oppositely
facing pattern receiving face; providing a second, initial pattern
forming tool having a generally cylindrical pattern defining
surface; relatively reciprocating and rotating said pattern
defining surface of said second initial pattern forming tool and
said additional pattern receiving face of said forming die blank;
engaging said generally cylindrical pattern defining surface of
said second initial pattern forming tool with said additional
pattern receiving face of said pattern forming die; urging said
generally cylindrical pattern defining surface of said second
initial pattern forming tool into said additional pattern receiving
face of said forming die blank to impress the pattern of said
generally cylindrical pattern defining surface of said second
initial pattern forming tool into said additional pattern receiving
face of said forming die blank; providing a second subsequent
pattern forming tool having a generally cylindrical pattern
defining surface; relatively reciprocating and rotating said
pattern defining surface of said second subsequent pattern forming
tool and said additional pattern receiving face of said forming die
blank; engaging said generally cylindrical pattern defining surface
of said second subsequent pattern forming tool with said additional
pattern receiving face of said pattern forming die after the
pattern of said generally cylindrical pattern defining surface of
said second initial pattern forming tool has been impressed into
said additional pattern receiving face of said forming die blank;
and urging said generally cylindrical pattern defining surface of
said second subsequent pattern forming tool into said additional
pattern receiving face of said forming die blank to impress the
pattern of said generally cylindrical pattern defining surface of
said second subsequent pattern forming tool into said additional
pattern receiving face of said forming die blank.
12. An apparatus for roll forming the face pattern onto a pattern
forming die comprising: a platen for supporting a forming die blank
having a pattern receiving face; an initial pattern forming tool
having a generally cylindrical pattern defining surface; a drive
mechanism for relatively reciprocating and rotating said pattern
defining surface of said initial pattern forming tool and said
pattern receiving face of said forming die blank; and relative
movement mechanism for engaging said generally cylindrical pattern
defining surface of said initial pattern forming tool with said
pattern receiving face of said pattern forming die for urging said
generally cylindrical pattern defining surface of said initial
pattern forming tool into said pattern receiving face of said
forming die blank to impress the pattern of said generally
cylindrical pattern defining surface of said initial pattern
forming tool into said pattern receiving face of said forming die
blank.
13. An apparatus for roll forming the face pattern onto a pattern
forming die as claimed in claim 12, further comprising: said
relative movement mechanism configured to maintain a constant force
between said engaged generally cylindrical pattern defining surface
of said initial pattern forming tool and said pattern receiving
face of said pattern forming die during said relative reciprocal
and rotational movement therebetween.
14. An apparatus for roll forming the face pattern onto a pattern
forming die as claimed in claim 12, further comprising: a
subsequent pattern forming tool having a generally cylindrical
pattern defining surface; a drive mechanism for relatively
reciprocating and rotating said pattern defining surface of said
subsequent pattern forming tool, and said pattern receiving face of
said forming die blank; relative movement mechanism for engaging
said generally cylindrical pattern defining surface of said
subsequent pattern forming tool with said pattern receiving face of
said pattern forming die after the pattern of said generally
cylindrical pattern defining surface of said initial pattern
forming tool has been impressed into said pattern receiving face of
said forming die blank for urging said generally cylindrical
pattern defining surface of said subsequent pattern forming tool
into said pattern receiving face of said forming die blank to
impress the pattern of said generally cylindrical pattern defining
surface of said subsequent pattern forming tool into said pattern
receiving face of said forming die blank.
15. An apparatus for roll forming the face pattern onto a pattern
forming die as claimed in claim 14, further comprising: said
relative movement mechanism configured to maintain a constant force
between said engaged generally cylindrical pattern defining surface
of said subsequent pattern forming tool and said pattern receiving
face of said pattern forming die during said relative reciprocal
and rotational movement therebetween.
16. An apparatus for roll forming the face pattern onto a pattern
forming die as claimed in claim 13 wherein said generally
cylindrical pattern defining surface of said initial pattern
forming tool comprises a spiral thread pattern of ridges defining
roots and crests.
17. An apparatus for roll forming the face pattern onto a pattern
forming die as claimed in claim 14, wherein said generally
cylindrical pattern defining surface of said initial pattern
forming tool comprises a spiral thread pattern of ridges defining
roots and crests, and wherein said generally cylindrical pattern
defining surface of said subsequent pattern forming tool comprises
a spiral pattern of ridges defining roots and crests, such that the
included angle of said ridges on said generally cylindrical pattern
defining surface of said subsequent pattern forming tool is a
greater included angle than the included angle of said ridges on
said generally cylindrical pattern defining surface of said initial
pattern forming tool.
18. An apparatus for roll forming the face pattern onto a pattern
forming die as claimed in claim 17, wherein the included angle of
said ridges on said generally cylindrical pattern defining surface
of said initial pattern forming tool is thirty degrees
(30.degree.), and wherein the included angle of said ridges on said
generally cylindrical pattern defining surface of said subsequent
pattern forming tool is sixty degrees (60.degree.).
19. An apparatus for roll forming the face pattern onto a pattern
forming die as claimed in claim 12, wherein said platen of said
relative movement mechanism is stationary and said drive mechanism
rotates and reciprocates said initial pattern forming tool relative
thereto.
20. An apparatus for roll forming the face pattern onto a pattern
forming die as claimed in claim 17, wherein said platen of said
relative movement mechanism is stationary and said drive mechanism
rotates and reciprocates said initial pattern forming tool and said
subsequent pattern forming tool relative thereto.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority pursuant to Title 35 USC
Sec. 119(e) to U.S. Provisional Application No. 61/708,939, filed
Oct. 2, 2012, for "Method and Apparatus for Cold Forming Thread
Rolling Dies," the entire contents of which are hereby incorporated
by reference herein as if fully set forth.
BACKGROUND
[0002] This disclosure relates to the roll forming of dies used to
manufacture threaded fasteners or other patterned cylindrical
articles. More particularly, it relates to the apparatus and method
for forming the pattern on the dies using a cold forming machine
and process.
[0003] Thread forming dies used in thread rolling are universally
produced using milling and grinding equipment. Such operations
usually take hours to produce a die set. Also, milling and grinding
produces dies having a rough surface.
[0004] Typically thread forming tooling includes a stationary die
and a moveable die. The face of the moving die is planar. The face
of the stationary die is contoured to provide specific areas of
engagement with the blank being formed into a fastener. The die
blank 50 is M-2 tool steel fully annealed having a hardness of
Rockwell 20 to 30. After forming the thread pattern on the die
blank, it is heat treated to a hardness of Rockwell C-60.
[0005] The die blanks are rectangular blocks of steel with die
faces impressed with a thread rolling pattern. To extend useful die
life, the thread rolling pattern is created on both faces of the
die blank. Once a given face is worn, the die block is rotated one
hundred eighty degrees (180.degree.) to present a fresh thread
forming pattern.
[0006] The root sharpness specification for dies has traditionally
been driven by die manufacturing limitations. Mills and grinding
wheels have a minimum capability to hold a fine tip, and as the tip
to be formed on a die gets sharper, their lifespan decreases
dramatically.
[0007] It has been determined that thread rolling dies may be
produced by cold forming die blanks with the ridges defining the
thread pattern. Disclosed is a machine and process of reduced
complexity and increased speed (minutes vs. hours). The resultant
thread forming die is of close tolerance and high wear
resistance.
[0008] It must be understood that the cold forming of thread
defining ridges on a thread rolling die as disclosed herein is
merely exemplary of the capabilities of the equipment, and process
disclosed. It is contemplated that the process and equipment is
suitable for other uses where deforming metal to provide a pattern
upon a surface is the desired result.
SUMMARY OF THE DISCLOSURE
[0009] In the development of the disclosed thread die cold forming
process and the equipment to produce cold formed thread rolling
dies, several important process limitations and consequences were
recognized.
[0010] First, it was recognized that it is necessary to roll a
round tool longitudinally across the surface of the workpiece
rather than trying to stamp threads onto it with a flat die moving
perpendicular to the die face. Longitudinal movement of a
cylindrical die allows the tool to form the thread pattern in
concentrated regions, gradually propagating the shape across the
die face. Much greater material flow can be achieved through this
rolling motion than stamping.
[0011] The direction of rolling must be at a low angle with respect
to the direction of the threads which are nearly parallel to the
longitudinal edge of the blank. Using a tool with a sufficiently
large diameter, it is possible to roll parallel to the edge of the
workpiece rather than parallel to the threads themselves. The
resultant tooling includes helical ridges like a screw, as opposed
to annular ridges in the form of annular rings. This makes the
process practical even for complex threadforms. For example, dies
for screws that have special threads at the tip can be formed all
at once instead of one thread at a time, as conventional methods
require.
[0012] Second, it was recognized that the tool must be rolled over
the workpiece multiple times, gradually developing deeper and
deeper threads. This keeps the stress in the tool low enough to
prevent breakage, spreading the work out over many small passes. It
is possible to develop a regimen in which a certain number of
passes are made, each at a certain, gradually increasing, downward
force.
[0013] Third, it was determined that it was necessary to trap the
workpiece rigidly along the two longitudinal sides parallel to the
direction of rolling. Without such confinement, workpiece material
flows sideways, perpendicular to the threads on the tool, breaking
them along the edge of the die face. Preventing this sideways
material flow protects the tool and enables the workpiece material
to flow up into the threads of the tool and develop into the
correct shape.
[0014] Fourth, it was concluded that a sixty degree (60.degree.)
threadform (the angle of the threads on all machine screws) is too
blunt to be fully formed with a single tool, even after utilizing
the concepts of rolling with multiple passes. No matter how many
passes are made, there is a limit to how much the threadform can be
developed. Therefore, it is necessary to use multiple tools in
sequence. First, a pre-form threadform is applied, such as one with
a thirty degree (30.degree.) or forty-five degree (45.degree.)
angle. Such a shape can be formed with full thread depth into the
die face. Then, a second tool with the final sixty degree
(60.degree.) threadform can be used to finish the desired shape of
the thread forming ridges of the final die configuration.
[0015] A secondary consequence of using multiple tools in sequence
(such as ones with 30.degree. and 60.degree. threads) is that the
thread on the workpiece that is left by first tool can be further
deformed by the second tool to form a shape on the workpiece that
is different from the shape of either tool. This can produce
threadforms that would otherwise be impossible to achieve, either
through forming or conventional methods. One example is a sharper
root, which enhances die performance beyond that of dies made with
conventional methods. The deeper die root allows the threads being
rolled onto a screw blank to expand freely instead of eventually
touching the root of the die. This results in a final screw product
with less crest damage due to contact with the die root. It also
extends die longevity.
[0016] It has also been determined that the coefficient of friction
between the cylindrical tool and workpiece is very important in
terms of the number of passes required to develop the thread form
on the die and the lifespan of the cold forming tool. Also,
specific coatings on the tool make a large difference in
performance. Therefore, it is contemplated that the cold forming
tool be coated with a hard, smooth, carbon based coating.
[0017] Cold forming of thread dies can be carried out on simple,
inexpensive, relatively small machines, especially when compared,
for example, to crush grinders. And, cold forming does not require
coolant, or remove material, which is a coolant contaminant.
Moreover, with cold forming, each tool can create multiple dies
before being to be replaced or reshaped, unlike mills and grinding
wheels.
[0018] The disclosed cold forming process utilizes force control
rather than dimensional positioning, for shape formation onto a die
blank. This permits the tooling to follow complex die contours
easily and accurately without the need for complicated fixturing,
setup, and machine programming. Moreover, as explained later, it is
contemplated that multiple die faces may be processed
simultaneously.
[0019] The die of the disclosed cold forming process has a very
smooth finish thereby reducing friction during use, and extending
die life. The smooth finish also contributes to manufacture of
fastener products with lower tolerance variation.
[0020] With cold forming, the final die root shape can be sharper
than the forming tools used to create it. As a result, the die root
sharpness specification may be based on die life considerations
rather than the frailties of the tools used to make the dies.
[0021] In this regard, a method is disclosed for roll forming the
face pattern onto a pattern forming die having a pattern receiving
face, using an initial, and subsequent, pattern forming tool, each
with a generally cylindrical pattern defining surface, by
relatively and sequentially reciprocating and rotating the pattern
defining surfaces and the pattern receiving face while engaging
them and urging them to impress the pattern of the pattern defining
surfaces into the pattern receiving face of the forming die blank.
An apparatus for performing the process is disclosed which includes
a platen for the pattern forming die, initial and subsequent
pattern forming tools each having a generally cylindrical pattern
defining surface, a drive mechanism for relatively and sequentially
reciprocating and rotating the pattern defining surfaces and the
pattern receiving face of the forming die blank, and relative
movement mechanism for engaging the surfaces to impress the pattern
of the pattern defining surfaces of the pattern forming tools into
the pattern receiving face of the forming die blank.
DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a side perspective view of a blank for a thread
forming die;
[0023] FIG. 2 is an end perspective view of a thread forming die
produced by cold forming employing the disclosed device and
process;
[0024] FIG. 3 is a perspective view of the thread forming apparatus
of the present disclosure;
[0025] FIG. 4 is a side view of the thread forming apparatus of the
present disclosure;
[0026] FIG. 5 is a partially broken away side view of the cold
forming apparatus of the present disclosure;
[0027] FIG. 6 is a side perspective view of the pattern forming
tool of the present disclosure coacting with a thread forming die
to which a thread form is imparted;
[0028] FIG. 7 is an end perspective view of the pattern forming
tool of the present disclosure and the thread forming die of FIG.
6;
[0029] FIG. 8 is a fragmentary sectional view on an enlarged scale
of an initial thread forming tool of the present disclosure and the
thread forming die being created;
[0030] FIG. 9 is a fragmentary sectional view on an enlarged scale
of a subsequent thread forming tool of the present disclosure and
the thread forming die being created;
[0031] FIG. 10 is a side view of an alternative configuration of an
apparatus for cold forming dies in accordance with the
disclosure.
DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS
[0032] A die blank or die block 50 to be processed is illustrated
in FIG. 1. The oppositely facing front and back elongate pattern
receiving faces 52 and 53 of the die blank are plain. These
rectangular faces receive the thread forming ridges which, in use,
impart a rolled thread to a cylindrical fastener blank. Opposite
longitudinal ends of face 52 may include a slight taper 55 of about
five degrees (5.degree.) for roll-on and roll-off of a blank to be
formed during thread rolling.
[0033] FIG. 2 illustrates a completed thread forming die 60 to be
used in roll forming threaded fasteners such as machine screws.
Here face 52 is impressed with a thread form pattern 54 that
progresses in a spiral pattern longitudinally along the face 52. A
similar ridge pattern may be provided on face 53 as well.
[0034] A machine for cold rolling thread forming dies is seen in
FIG. 3. The machine 100 is illustrated somewhat schematically in
FIGS. 4 and 5. Machine 100 comprises relative movement mechanism,
drive mechanism, and tooling.
[0035] Referring to FIGS. 3 and 4, machine 100 includes a base 101,
supporting a platen 102 which is an element of the relative
movement mechanism. It supports a die blank 50 for processing by
rotatable cylindrical tools 200 and 300 which are employed
sequentially as will be explained. The platen 102 includes vertical
side blocks 106 that support the longitudinal edges of the die
blank 50.
[0036] The base 101 includes longitudinal rails 108. A
longitudinally slidable head 110 is slidably supported on rails 108
of base 101 by interengaged rails 116 shown in FIG. 4. Drive
mechanism includes a linear actuator driven by a servo motor 111
(See FIG. 3) includes a rotatable threaded shaft 118 supported on
base 101 and threaded follower block within head 110. It provides
reciprocal movement of head 110 by activation of the servo motor
111. The path of reciprocal movement is sufficiently long for the
tool 200 or 300 to traverse the entire surface 52 of die blank
50.
[0037] As illustrated in FIG. 4, positioning mechanism includes
vertically movable by hydraulic actuators 103 that urge the platen
102 and attached die blank upward. The hydraulic actuators 103
raise the exposed face 52 of die blank 50 into operative engagement
with the pattern forming tools 200 and 300. The amount of
engagement of the pattern forming tools 200 and 300 with the face
52 of the blank 50 is controlled by the force imparted by the
hydraulic actuators 103 to ensure cold forming deformation proceeds
at the desired rate. Force may be increased as cold forming
progresses up to 40,000 pounds or higher.
[0038] Since the interengagement of the pattern forming tools 200
and 300 and face 52 of die blank is controlled by force (as opposed
to distance or interference) by maintaining a constant force it is
possible to cold form the die blank even though the face is not
planar, as is common in the stationary die profile and as is
illustrated in FIG. 1.
[0039] In the machine of the present disclosure, two tools, initial
pattern forming tool 200, and subsequent pattern forming tool 300
are utilized, sequentially, to create a thread rolling die thread
form 54 on the face 52 of a blank 50. As an element of the drive
mechanism, head 110 carries servo motor 112 that rotates a tool
shaft 114 at a first tool station. The rotatable shaft 114 drives
initial pattern forming tool 200. As a further element of the drive
mechanism, head 110 also carries a further servo motor 113 that
rotates a second tool shaft at a second tool station (See FIG. 5).
The second rotatable shaft 115 drives subsequent pattern forming
tool 300. The motor 111 driving the head linear actuator and the
servo motors 112, 113 driving tool shafts 114, 115 are synchronized
to rotate initial pattern forming tool 200 and subsequent pattern
forming tool 300 reciprocally across a die face 52 at the
appropriate speed and orientation to insure a rolling relationship
without slippage.
[0040] The pattern forming tools 200 and 300 are sequentially
placed in engaging contact with the pattern receiving face 52 of
die blank 50. That is, subsequent pattern forming tool 300 is
employed after deformation of the pattern receiving face 52
employing initial pattern forming tool 200 is complete. In each
instance, the amount of interference or engagement of the pattern
on the pattern forming tool 200 or 300 is controlled by positioning
of the profile 202 or 302 relative to the pattern receiving face 52
of die 50. Using cylinders 103 it is contemplated that a given
predetermined interference results in a particular force
requirement to maintain the engagement as the pattern forming tool
reciprocally traverses the pattern receiving face in rolling
engagement. Such force requirement is reflected, for example, by
the output torque of the drive servo motor 112 or 113. The force to
maintain the requisite interference may therefore be recognized by
monitoring servo motor output torque. It is then controlled by
maintaining that torque at a constant level by adjustment of the
force applied by cylinders 103 to create the interference or
engagement. In this manner, the force may be maintained constant
regardless of the surface profile of face 52.
[0041] As deformation of face 52 progresses, the force requirement
would decrease. By adjustment of the cylinder pressure of cylinders
103, the interference can be readjusted to attain the predetermined
force requirement.
[0042] Seen in FIGS. 6 and 7, initial pattern forming tool 200 is a
cylinder, with a ridge profile 202 impressed upon its outer
cylindrical surface. Similarly subsequent pattern forming tool 300
is a cylinder with a ridge profile 302 impressed on its outer
surface. The tools are formed by milling, grinding and polishing
(See FIGS. 5, 8 and 9).
[0043] The initial pattern forming tool 200 includes thread forming
ridges 202 to impart an initial thread form to the face 52 of the
thread rolling die 50. These ridges extend in a spiral pattern
around the outer cylindrical surface of the tool. As the tool
reciprocates longitudinally along the longitudinal length of the
face 52 of the die blank 50 it deforms the blank in accordance with
the pattern on the tool 200, and the interference between the tool
and blank. As multiple reciprocal passes across the blank proceed,
the interference is increased until the desired pattern is
achieved. It is contemplated that tool 200 may execute forty (40)
or more passes to impress the thread forming pattern onto surface
52.
[0044] The subsequent pattern forming tool 300 includes thread
forming ridges 302 to impart a final thread form to the face 52 of
the thread rolling die 50. The ridges extend in a spiral pattern
around the outer cylindrical surface of the tool. As the tool
reciprocates longitudinally along the longitudinal length of the
face 52 of the die blank 50 it deforms the blank in accordance with
the pattern on the tool 300, and the interference between the tool
and blank. As multiple reciprocal passes across the blank proceed,
the interference is increased until the desired pattern is
achieved. It is contemplated that tool 300 may execute forty (40)
or more passes to impress the thread forming pattern onto surface
52.
[0045] As seen in FIG. 8, the initial pattern forming tool 200
includes an initial thread profile 202 with ridges formed at an
included angle of about thirty degrees (30.degree.) or forty-five
degrees (45.degree.). This tool is used to provide initial
deformation of the face 52 of the thread rolling die blank 50.
Thereafter, as illustrated in FIG. 9, a subsequent pattern forming
tool is provided with a final ridge profile 302 intended to impart
the final shape to the thread form on the face of die blank 50. The
ridges on the subsequent pattern forming tool 300 are formed at an
included angle of sixty degrees (60.degree.). These ridges are
configured to define the root and crest profile of the intended
fastener thread onto the face 52 of the die blank 50.
[0046] The subsequent cylindrical tool 300 may be powered by a
second servo motor 113 at a second tool station on the same base.
The second tool station is essentially identical to the first tool
station and operates in the same way. Alternatively, only one tool
station need by employed and the pattern forming tools 200 and 300
interchanged on the same shaft as needed.
[0047] In the embodiment illustrated, the platen 102 is slidable
along base 101 to orient it with the second tool station. Such an
arrangement is illustrated in FIG. 5, which also schematically
depicts an arrangement where the force imparting cylinders 103 are
mounted within the slidable head 110, rather than the stationary
base 101.
[0048] A further modified form of cold forming die is illustrated
in FIG. 10. Here the pattern of thread forming ridges are
simultaneously impressed upon both front and back faces 52 and 53
of die blank 50. The die blank 50 is held stationary on a platen
502 with opposite rectangular faces 52 and 53 exposed.
[0049] The machine 500 is equipped with two sets of opposed
cylindrical pattern forming tools 600 and 700. These tools are
driven by servo motors in synchronization with reciprocal movement
of the head 510 relative to base 501. Actuators 503 urge the tools
into operative contact with both longitudinal surfaces 52 and 53 of
the die blank 50 to roll thread pattern onto both faces
simultaneously. In this embodiment, it is contemplated that tools
600 and 700 are the same as initial pattern forming tool 200 and
impress an initial, pattern on faces 52 and 54 with, for example, a
thirty degree (30.degree.) thread profile. Thereafter, a pair of
subsequent pattern forming tools identical to tool 300 with a
60.degree. ridge cross section would be used to finish the thread
configuration on faces 52 and 54. These subsequent pattern forming
tools would, for example, replace tools 600 and 700 in the machine
500 for the final rolling operation.
[0050] Variations and modifications of the foregoing are within the
scope of the present invention. It is understood that the invention
disclosed and defined herein extends to all alternative
combinations of two or more of the individual features mentioned or
evident from the text and/or drawings. All of these different
combinations constitute various alternative aspects of the present
invention. The embodiments described herein explain the best modes
known for practicing the invention and will enable others skilled
in the art to utilize the invention. The claims are to be construed
to include alternative embodiments to the extent permitted by the
prior art.
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